[postgis-users] ST_Buffer + grid problem
Ed Linde
edolinde at gmail.com
Thu Mar 22 07:23:04 PDT 2012
Yeah only problem being that I don't know which geometry is the one that
fails... its a table with 300K geometries.
Have never written any PgSQL, so this I guess would require a loop to check
which OSM ID its failing on. Unless
you got a good idea to pin-point this error?
On Thu, Mar 22, 2012 at 3:16 PM, Pierre Racine
<Pierre.Racine at sbf.ulaval.ca>wrote:
> What I mean is to replace:
>
> SELECT ST_AsRaster(ST_Extent(way_geom)::geometry, 0.000036, 0.000036) rast
> FROM buffers where osm_id = 94695311
>
> by something like:
>
> SELECT ST_AsRaster(ST_GeomFromText('POLYGON((11.1539754732244
> 55.5772503545236,11.1540114732244 55.5772503545236,11.1540114732244
> 55.5772863545236,11.1539754732244 55.5772863545236,11.1539754732244
> 55.5772503545236))'), 0.000036, 0.000036)
>
> with one of the geometry reproducing the bug so we don't need your dataset
> to test and reproduce.
>
> Pierre
>
> > -----Original Message-----
> > From: manohar.kaul at gmail.com [mailto:manohar.kaul at gmail.com] On Behalf
> > Of Ed Linde
> > Sent: Thursday, March 22, 2012 9:59 AM
> > To: Pierre Racine
> > Cc: PostGIS Users Discussion; Bborie Park (bkpark at ucdavis.edu)
> > Subject: Re: [postgis-users] ST_Buffer + grid problem
> >
> > sure. Did you mean ST_GeomfromText or show it as text?
> >
> > SELECT ST_GeomfromText ((gvxy).geom), ((gvxy).x - 1) * rwidth + (gvxy).y
> gridid
> > FROM (SELECT ST_PixelAsPolygons(rast) gvxy, ST_Width(rast) rwidth
> > FROM (SELECT ST_AsRaster(ST_Extent(way_geom)::geometry,
> 0.000036,
> > 0.000036) rast
> > FROM buffers
> > where osm_id = 94695311
> > ) foo1
> > ) foo2;
> >
> > ERROR: parse error - invalid geometry
> > HINT: "010300000001000000050000005" <-- parse error at position 27
> within
> > geometry
> >
> > ********** Error **********
> >
> > ERROR: parse error - invalid geometry
> > SQL state: XX000
> > Hint: "010300000001000000050000005" <-- parse error at position 27 within
> > geometry
> >
> >
> >
> > On Thu, Mar 22, 2012 at 2:53 PM, Pierre Racine <
> Pierre.Racine at sbf.ulaval.ca>
> > wrote:
> >
> >
> > I guess this is related to a GDAL problem where you cannot create a
> > raster using ST_AsRaster with pixel size smaller than 1. Was this fixed
> Bborie?
> >
> > Ed could you reduce the list of geometries passed to ST_Extent to
> one
> > and write it as ST_GeomfromText so we can debug this more easily?
> >
> >
> > Pierre
> >
> > > -----Original Message-----
> > > From: manohar.kaul at gmail.com [mailto:manohar.kaul at gmail.com]
> > On Behalf
> > > Of Ed Linde
> >
> > > Sent: Thursday, March 22, 2012 9:45 AM
> > > To: Pierre Racine
> > > Cc: PostGIS Users Discussion
> > > Subject: Re: [postgis-users] ST_Buffer + grid problem
> > >
> > > Hi Pierre,
> >
> > > So I am trying to have a 4meter by 4meter cell and I converted
> > 4meters to
> > > degrees, because I think ST_Extent will compute it in degrees as
> my
> > geometry is
> > > in srid 4326. But I get this GDAL error which I have no clue
> what it
> > means. Any
> > > ideas how I can fix it? Also I noticed that if I set it to 1.0,
> 1.0 I get
> > > 21 rows but the gridid isn't continuous either (which is weird).
> > >
> > > CREATE TABLE vectorgrid AS
> > > SELECT (gvxy).geom, ((gvxy).x - 1) * rwidth + (gvxy).y gridid
> FROM
> > (SELECT
> > > ST_PixelAsPolygons(rast) gvxy, ST_Width(rast) rwidth
> > > FROM (SELECT
> ST_AsRaster(ST_Extent(way_geom)::geometry,
> > 0.000036,
> > > 0.000036) rast
> > > FROM buffers
> > > ) foo1
> > > ) foo2;
> > >
> > > ERROR: rt_raster_gdal_rasterize: Unable to add band to
> GDALDataset
> > >
> > > ********** Error **********
> > >
> > > ERROR: rt_raster_gdal_rasterize: Unable to add band to
> GDALDataset
> > SQL state:
> > > XX000
> > >
> > >
> > >
> > >
> > > On Thu, Mar 22, 2012 at 2:13 PM, Pierre Racine
> > <Pierre.Racine at sbf.ulaval.ca>
> > > wrote:
> > >
> > >
> > > You can control how the grid is aligned by using more
> ST_AsRaster
> > > parameters. See:
> > >
> > > http://postgis.refractions.net/documentation/manual-
> > > svn/RT_ST_AsRaster.html
> > >
> > > If you want it to align on your point, just align it on
> your points...
> > >
> > > Pierre
> > >
> > >
> > > > -----Original Message-----
> > > > From: manohar.kaul at gmail.com
> > [mailto:manohar.kaul at gmail.com]
> > > On Behalf
> > > > Of Ed Linde
> > > > Sent: Thursday, March 22, 2012 9:05 AM
> > > > To: PostGIS Users Discussion
> > > > Cc: Pierre Racine
> > > > Subject: Re: [postgis-users] ST_Buffer + grid problem
> > > >
> > > > Hi Pierre,
> > > > Thanks for the grid idea last night. I have a problem
> though, I
> > want to
> > > have a 4m
> > > > by 4m cell sized grid over my buffer geometries which
> are in SRID
> > =
> > > 4326. And
> > > > then I have another data set of 2D points which are also
> in SRID
> > > 4326...
> > > > wondering how I can figure out from just a given
> (lat,long) which
> > cell
> > > ID in the
> > > > buffer grid it would belong to? I am thinking that I
> might run into
> > > "alignment
> > > > issues" because shouldn't the extent of the grid be
> exactly the
> > same
> > > on the 2D
> > > > point cloud as well, so that the grid cell IDs will
> match? Unless I
> > am
> > > missing
> > > > something here?
> > > >
> > > > Cheers,
> > > > Ed
> > > >
> > > >
> > > >
> > > > On Wed, Mar 21, 2012 at 8:46 PM, Pierre Racine
> > > <Pierre.Racine at sbf.ulaval.ca>
> > > > wrote:
> > > >
> > > >
> > > > > I am not sure if this is possible, but I have
> computed (using
> > > ST_Buffer)
> > > > a sort of
> > > > > buffer around several LINESTRINGs. Now I would
> like to lay
> > some
> > > sort
> > > > of grid of
> > > > > say 1m^2 cell size on top of this collection of
> geometries
> > and
> > > then
> > > > compute the
> > > > > intersection... so in the end I would like to
> for example,
> > know
> > > that grid
> > > > cell ID = 1
> > > > > intersects with buffers 1 and 10, grid cell 2
> intersects with
> > buffers
> > > 7, 10
> > > > etc..
> > > > >
> > > > > Is there a simple way of doing this in postgis?
> Maybe
> > someone
> > > could
> > > > point me to
> > > > > some documentation of how I can generate such a
> grid in
> > postgis
> > > and
> > > > maybe
> > > > > then I can use just ST_Intersect once I have
> these two
> > > geometries?
> > > >
> > > >
> > > > With the raster type you can now easily create a
> vector grid
> > like
> > > this:
> > > >
> > > > CREATE TABLE vectorgrid AS
> > > > SELECT (gvxy).geom, ((gvxy).x - 1) * rwidth +
> (gvxy).y gridid
> > > > FROM (SELECT ST_PixelAsPolygons(rast) gvxy,
> ST_Width(rast)
> > > rwidth
> > > > FROM (SELECT
> > ST_AsRaster(ST_Extent(geom)::geometry,
> > > 1.0,
> > > > 1.0) rast
> > > > FROM yourbuffertable
> > > > ) foo1
> > > > ) foo2;
> > > >
> > > > Make sure a spatial index exist on both tables:
> > > >
> > > > CREATE INDEX yourbuffertable_geom_idx ON
> > yourbuffertable
> > > USING
> > > > gist (geom);
> > > > CREATE INDEX vectorgrid _geom_idx ON vectorgrid
> USING
> > gist
> > > > (geom);
> > > >
> > > > You can then perform a normal intersect query:
> > > >
> > > > CREATE TABLE interresult AS
> > > > SELECT b.bufferid, g.gridid,
> ST_Intersection(g.geom, b.geom)
> > > geom
> > > > FROM vectorgrid g, yourbuffertable b
> > > > WHERE ST_Intersects(g.geom, b.geom);
> > > >
> > > > Pierre
> > > > _______________________________________________
> > > > postgis-users mailing list
> > > > postgis-users at postgis.refractions.net
> > > >
> http://postgis.refractions.net/mailman/listinfo/postgis-users
> > > >
> > > >
> > >
> > >
> > >
> >
> >
> >
>
>
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